Land Rover 4.3 V8 - revision and tuning

[Chris]

Hi all

First of all, I'd like to introduce myself.
My name is Christoph, I'm 35 years of age, German, based in Basel, Switzerland and having had a spleen for Range Rover Classics since I was a little boy.

Currently, I own 5 of them in varying states of rot and shine

back to topic:

I recently bought a 4.3 engine out of a RRC LSE, which I'm going to rebuild and - hopefully power/torque tune to suite one of my RR.

CR question

As the 4.3 engine has a standard CR of 8.95 : 1, I'd like to go for 10:1 or 10.5:1.

What will be the best way to go for? Head skimming? Block skimming?
Different pistons?


Camshaft question:

Does anyone know Kent cams H180 (symmetrical) and H200 (assymmetrical)?
Which one would you go for in a Range Rover with auto transmission?

Thanks and kind regards
Christoph

[garrycol]

I recently bought a 4.3 engine out of a RRC LSE,

Thanks and kind regards
Christoph

Just a minor clarification - if the engine is out of a RRC LSE it will be the 4.2 engine (4,275 cc) rather than the 4.3 (4,280 cc) which is out of a TVR. Other than the little 5cc difference I am not sure what other differences may be in the block etc but I believe the major differences are in the heads where the TVR breathes a lot better.

Not sure if this impacts on what you are planning.

Oh - and welcome to the forum - some great information to be had here.

Cheers

garry

[Rossco]

If it's on composite head gaskets you could swap over to tin head gaskets. You'll pick up a full point of compression just by doing that.

[Chris]

Hi

It's from a RRC.

Head gaskets are tin already, so no easy improvement to be found here.

Is there a thumb rule to estimate CR inrease after skimming? e.g. 0.1mm less means 0.1 more CR?

If it's on composite head gaskets you could swap over to tin head gaskets. You'll pick up a full point of compression just by doing that.

[ChrisJC]

If you skim the heads a lot, then the inlet manifold is too wide, and the valley gasket won't fit any more either.

Rover changed the compression with different pistons. I don't know if there are options for the 4.2L engine.

Chris.

[Rossco]

Rover changed the compression with different pistons. I don't know if there are options for the 4.2L engine.

Chris.

Not aware of any piston options for the 4.2L

[Chris]

How much effect would have the smaller combustion chambers (28cc) of the late engines? (when using the same head gasket)

1 point? 9:1 to 10:1?

[Rossco]

That would give you at least a full point if you stayed with tin gaskets

http://www.not2fast.com/turbo/compressi ... sion.shtml

[garrycol]

The 4.2 and 4.3 engines have the same bore as the 3.9, 4.0, 4.6 and 5.0 engines (94mm).

The 4.0 and 4.6 engines have both LC and HC pistons and indeed if you put 4.0 LC pistons in a 4.6 you get a compression ratio between the 4.6 LC and HC compression ratios. If 4.0 HC pistons went in the comp ratio would probably higher than a 4.6 HC.

My point is that by putting in other 4.0/4.6 pistons you may be able to achieve a higher compression ratio. However it will require a bit of research and a lot of calculations.

I recently built a 4.6 and only had 4.0LC and 4.6LC pistons - I put in the 4.0 LC pistons which in the 4.6 give it a comp ratio of about 9.2:1 up from the standard 8.15:1

It will need a bit of research.

Garry

[Rossco]

Bores are the same in the 4.2, 4.0, and 4.6 but rods are different between the 4.2 and the other two. Different wrist pins and big ends

[Chris]

Just a quick one:

Are the cylinder heads interchangeable from side to side or dedicated left/right castings?

[russell_ram]

Identical and completely interchangeable side to side.

[DEVONMAN]

It's possible to fit 3.9 pistons into a 4.2 but you need to machine their tops to put them just below the deck. This then gives you a piston with a reduced dish and the compression ratio will be higher. I don't know the number though.

The top ring will however be closer to the crown but unless you are going forced induction or nitrous it should not be a problem.

[carsy]

It's possible to fit 3.9 pistons into a 4.2 but you need to machine their tops to put them just below the deck. This then gives you a piston with a reduced dish and the compression ratio will be higher. I don't know the number though.

The top ring will however be closer to the crown but unless you are going forced induction or nitrous it should not be a problem.

This is what tvr did with their 4.3 motor. I imagine on tin gaskets you would be about there. For your wanted cr. Or use high comp 3.9's machined down with composite gaskets.

[Rossco]

I did a similar thing on a 3.5 with a 4.2 crank, that gives a nice 3.8 long stroke with high compression.

You may need to machine a little off the piston skirt as well because they can catch on the counterweights at BDC